In recent years a method for adding agricultural chemicals to farmland has developed. This method commonly known as "chemigation" involves the introduction of the agricultural chemicals into irrigation water with subsequent dispersion of the irrigation water containing the chemicals onto the cropland. Chemicals such as fertilizers, insecticides, herbicides, etc. can be dispersed by this method. In order to be effective, the chemical must be well dispersed in the irrigation water prior to the water being sprayed upon the cropland. Care must be taken in order to assure that in the event of a shutdown in the flow of irrigation water the chemical will not flow into the water source causing contamination of the source of water. Also, it is necessary that irrigation water does not flow into the chemical supply system causing overflow and area contamination.
Although some agricultural chemicals are soluble in water, it is also desirable to effectively disperse chemicals which are not readily soluble or are insoluble in water. These chemicals are often supplied dissolved in a water insoluble solvent such as kerosene. Certain chemicals such as fertilizers can also be available as a slurry of solids in a liquid. Therefore, it is desirable to effectively disperse a water insoluble (or minimally soluble) material into a stream of irrigation water.
A number of valve systems have been suggested in the prior art. Savage in U.S. Pat. No. 3,267,959 (1966) discloses a valve which is said to function as an anti-fouling and anti-siphoning valve in irrigation systems. The valve is provided with a neck portion which is designed to extend into the liquid stream being treated so that the chemicals being discharged will be "immediately absorbed by the liquid and removed from the positio of the valve proper." The valve is designed to open when the chamical being injected is subjected to a pressure equal to or greater than the sum of the pressure of the fluid flowing in the pipe into which the valve extends. An array of slots is provided in the tip portion so that when the chemical flows past the O-ring seal, the chemical can disperse through the slots thereby providing an early release of discharge pressure to avoid dislodging the O-ring seal. This valve has a significant disadvantage in that, when the flow rate of the chemical is increased and the valve member containing the O-ring travels past the end of the housing containing the slots, the valve stem can be subjected to a significant lateral force as the result of the flow of the liquid stream past the valve. This lateral force can bend the valve stem resulting in failure of the O-ring valve to seat properly. Deflection of the extended valve stem can also result in the valve jammping open. Either effect will allow the chemical to continue to leak into the system or allow liquid in the conduit to pass through the checkvalve back to the source of the chemical.
Gilroy in U.S. Pat. No. 4,437,611 (1984) discloses a spray nozzle to be used in a sprinkler system in a corrosive or dirty environment. The spray nozzle is designed to be mounted in a conduit wall essentially flush with the inside of the conduit into which a spray of liquid is to be provided. This nozzle has a disadvantage that the moving parts are continually bathed in the checmial being injected. Since many of the chemicals used in agriculture are corrosive, special materials must be used to avoid corrosion and plugging of the valve. Additionally, introduction of the chemical along the conduit wall does not provide for optimum dispersion of the chemical into the flowing stream.
In a series of three patents, Stamps et al. disclose a method and apparatus for dispersing substantially water soluble agricultural chemicals into an irrigation system. This method involves dispersing the chemical by passing a pressurized stream containing the chemical through an orifice. The dispersed stream passes through a checkvalve and subsequently through an entry line which projects into the water stream. This procedure has the disadvantage of requiring a substantial amount of additional equipment in order to effectively disperse the chemical into a stream which must then be dispersed into the main irrigation stream. U.S. Pat. Nos. 3,464,626 (1969), 3,326,232 (1967), and 3,375,976 (1968).
None of these references disclose a device capable of effectively dispersing a fluid at a variety of flow rates itno a moving stream of liquid. All of these referenced devices and methods have the disadvantages disclosed hereinabove. Accordingly, there is a need for an apparatus which can effectively disperse a fluid into a stream of a liquid while also serving as a checkvalve to avoid unintentional flow of the fluid into the liquid or the liquid back into the source of the fluid.